1. Field of the Invention
This invention relates to closed crankcase ventilation systems for internal combustion engines.
2. Background Art
The crankcase of an operating internal combustion engine is pressurized by blow-by gases (gases that flow past the piston rings, valve stems and turbo seals), and in the case of a two-cycle engine, by leakage from the air box. Venting is required to control crankcase pressure and thereby minimize oil leakage past crankshaft seals, oil pan gaskets, etc., and to prevent harmful liquids, including sulfuric acid, from condensing in the engine. The large quantity of lube oil contained in the crankcase, which may be extremely agitated under normal engine operating conditions, complicates the ventilation task. High temperature and agitation cause oil mist (vapor and droplets) to become entrained in the crankcase gases or effluent. This oil mist must be separated from the effluent prior to its discharge from the crankcase, to prevent loss of useful engine oil and environmental pollution. An effective crankcase ventilation system is one that controls crankcase pressure, and minimizes loss and contamination of the lube oil.
There are two types of crankcase ventilation systems commonly used in internal combustion engines. An xe2x80x9copenxe2x80x9d crankcase ventilation system discharges crankcase effluent gases to the atmosphere, while a xe2x80x9cclosedxe2x80x9d crankcase ventilation system avoids atmospheric discharge by piping the gases to the engine""s air inlet system, (typically upstream of the turbocharger compressor in a diesel engine).
The function of an open system is to vent effluent gases to the atmosphere, free from oil droplets. It must maintain minimal positive crankcase pressure throughout the normal wear life of the engine, while operating under all speeds, loads and operating attitudes for which the engine was designed. A closed system has the additional function of limiting vacuum in the crankcase through use of a valve or by allowing filtered fresh air into the engine. Diesel engines typically use a Crankcase Depression Regulator (diaphragm valve). Gasoline engines, which have lower blow-by flow rates than diesels, typically use PCV""s (Positive Crankcase Ventilation Valves).
The closed crankcase ventilation system has the added requirement of minimizing the inherent risk of carrying excessive oil (pull-over) into the air intake system. Any oil delivery to the air intake is considered undesirable oil consumption and increased exhaust emissions. Extreme oil pull-over can cause loss of engine control or over-speed if the oil is burned, or flooding of cylinders and hydrostatic lock, with associated damage (e.g., bent connecting rod or blown cylinder head gasket). Crankcase ventilation system design must ensure that the system (either open or closed) will function properly for the life of the engine, under all possible operating conditions, including operation at extreme tilt angles, increasing blow-by levels due to engine wear, air inlet restrictions, engine speeds, etc.
The quantity of effluent gas flowing through a crankcase ventilation system naturally increases over time as pistons, piston rings, cylinder lines, and other engine components wear. Failure of a cylinder component (e.g., scuffing, broken or burned ring, piston, etc.) can cause a drastic increase in effluent volume. Furthermore, a failure of a single cylinder may, if the engine is continued to operate, cause catastrophic engine failure due to secondary damage (e.g., connecting rod through the wall of the crankcase), or in the case of an engine with a closed crankcase ventilation system due to oil pull-over. With an open crankcase ventilation system, this flow increase results in increased crankcase pressure. Crankcase pressure monitors have been used successfully on engines with open crankcase ventilation systems to detect a cylinder failure, allowing the engine to be shutdown before major secondary damage occurs. On engines with a closed crankcase ventilation system, the system itself limits pressure increase thereby making crankcase pressure monitors ineffective. Another limitation of crankcase pressure monitors is that they are set for a single pressure, which if exceeded triggers a response; no information about the engine is given at various operating pressures below the preset limit.
Blow-by measurement is a commonly used diagnostic technique during engine development or for evaluating the condition of an engine in service. The usual method employed is to attach a gas flow meter to the engine ventilation system. High readings can indicate a worn out engine, loss of ring sealing, impending cylinder kit failure, or sealing problems in other engine systems (e.g., turbocharger).
Ever more stringent emission requirements have led to more effective oil separation in closed crankcase ventilation systems. Some systems already incorporate filters that need to be periodically replaced for proper operation. Engine oil consumed through recirculated effluent may someday have to be controlled through the life of an engine to ensure compliance with emission standards.
There is a need for a simple and cost effective system for continuous monitoring of engine blow-by gas flow, for use as a tool to evaluate the condition of an engine, and to diagnose problems associated with increased blow-by. There is a need to warn the engine operator of crankcase ventilation system malfunction or need to change filters (for fresh air or oil separation) in a closed crankcase ventilation system during normal engine operation. There is a need for detecting cylinder kit damage, particularly in closed crankcase ventilation systems, and of warning the operator or reducing engine power to avoid subsequent catastrophic engine failure. There may be a need in the future to monitor the amount of oil consumed through a closed crankcase ventilation system, or a need to detect an increased level of oil concentration in the effluent gas stream. The present invention is directed to providing such a system that addresses the above problems as summarized below.
According to one aspect of the invention, an internal combustion engine is provided with a closed crankcase ventilation system including a flow meter. The engine comprises at least one combustion chamber and a reciprocating piston. The combustion chamber has an exhaust port and an air intake on a first side of the piston and crankcase on a second side of the piston. The closed crankcase ventilation system recirculates a effluent gas stream from the crankcase to the air intake. At least one flow meter is disposed in the effluent gas stream to measure the volume of gas flowing through the ventilation system. A signal is produced by the flow meter that senses the volume of gas flow. The engine control system receives the signal indicative of the volume of gas flow and monitors the signal to provide a control system output based upon the sensed volume of gas flow. The control system output can then be sent to an engine operation log that electronically records the volume of gas flow as an engine diagnostic parameter. This blow-by history can indicate the amount of wear through the life of the engine. The control system output can be used to warn the operator of a sudden increase in blow-by, indicating that the engine is in need of service (e.g., to replace ventilation system filters or to correct other engine component malfunctions). The control system output can be used to reduce engine power or shut the engine down to prevent subsequent major damage that could occur following relatively minor damage to a cylinder, piston, piston ring or other engine component.
According to another aspect of the present invention a closed crankcase ventilation system is provided for an ignition engine having a crankcase, an air inlet, and an engine control. The internal combustion engine may be a compression ignition or spark ignition engine that may be turbocharged or naturally aspirated. The ventilation system is ported from the crankcase to the air intake system of the engine. A set of hoses direct an effluent gas stream from the crankcase to the air intake system. At least one flow meter is connected in fluid flow communication with the hoses to measure the air flow volume passing through the hoses. The measured effluent flow may be routed to the upstream side of a turbocharger compressor of a turbocharged engine or to the intake manifold of a naturally aspirated engine. The flow meter produces a signal indicative of air flow volume. The signal is provided to the engine control that monitors the signal to determine if the engine should be shut down or serviced.
According to other aspects of the invention the crankcase may be ported through a breather that may comprise one or more rocker cover breathers. Alternatively, the breather may comprise a flywheel housing breather, oil pan breather, cylinder block breather or gear case breather.
The flow meter may be an electronic air flow meter. More specifically, the flow meter may be a simple turbine type flow meter with a magnetic pick-up. Alternatively, the flow meter may be a mass flow sensor that is capable of detecting an increase in oil concentration in the effluent gas stream. In another alternative embodiment, the flow meter could be used in conjunction with a continuous pressure output sensor (crankcase pressure transducer). The flow meter and crankcase pressure transducer may offer a more cost effective system that would be capable of detecting an increase in oil concentration in the effluent gas stream.
These and other aspects of the present invention will be better understood in view of the attached drawings and following detailed description of a preferred embodiment of the invention.